Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32N O V E M B E R / D E C E M B E R 2 0 1 6 POTATO GROWER 21 With the continual precipitation we had this year, there are few potato acres spared from lenticel spot. As you may remember, potatoes are covered in these tiny slits called lenticels. Researchers have actually counted the number of lenticels and found that there can be a wide range from 28 to 274 lenticels per tuber. Growing conditions, be it dry or wet, do not affect lenticel num- ber. However, tuber size and cultivar do affect lenticel number. Larger tubers tend to have more lenticels then smaller tubers. In some European cultivars there have been differences reported in lenticel number. Lenticels are the gateway for gas exchange. Potato tubers need oxy- gen to grow and develop. However, lenticels can become an entry point for tuber diseases when they enlarge as a result of low oxygen in wet con- ditions. When lenticels are enlarged they can appear to be like small white ‘popcorn’ spots on the tuber surface (Figure 1) and when they dry they may appear as scab lesions (Figure 2). Once bacteria are present in the lenticel they can multiply and cause rotting of the tuber or the bacteria can enter a latent phase. The spotted lenticels (Figure 3) are a result of the latent phase caused when the lenticel closes and a corky layer is formed over the bacteria, but the tuber is not broken down by bacteria. Pectobacterium (soft rot) can sur- vive in a latent phase in lenticels until the next planting season. As a result, tubers infected with pathogens in the lenticels become less marketable because of the blem- ish and can lead to tuber breakdown if favorable conditions exist. Changes in temperature, moisture, and air quality may encourage lenticels to open and bacteria to multiply. To mitigate problems with lenticel spot, avoid harvesting low areas in the field. When piling tubers be sure to minimize bruising and dry the tubers down as quickly as possible to avoid lenticels staying too wet or getting too much CO2. When the potatoes are washed, ensure they are dried quickly and thoroughly, and ensure that bags and shipping containers are well ventilated. Andy’s Advice Lenticel Spot In Potato By Andy Robinson, Extension Potato Agronomist, NDSU/UMN Figure 1. Enlarged lenticels as a result of too much water. Figure 2. Dried lenticels appear as scab lesions. Figure 3. Spotted lenticels after wash- ing.